Example Python Module

From this stackoverflow Virtual Key Codes are at: MSDN See also this stackoverflow on unicode to see how to send unicode.

Also this stackoverflow on sending to a specific window

We use ctypes to call to user32.

import ctypes
from ctypes import wintypes
import time

user32 = ctypes.WinDLL('user32', use_last_error=True)

INPUT_MOUSE    = 0
INPUT_KEYBOARD = 1
INPUT_HARDWARE = 2

KEYEVENTF_EXTENDEDKEY = 0x0001
KEYEVENTF_KEYUP       = 0x0002
KEYEVENTF_UNICODE     = 0x0004
KEYEVENTF_SCANCODE    = 0x0008

MAPVK_VK_TO_VSC = 0

# msdn.microsoft.com/en-us/library/dd375731
VK_TAB  = 0x09
VK_MENU = 0x12

# C struct definitions

wintypes.ULONG_PTR = wintypes.WPARAM

class MOUSEINPUT(ctypes.Structure):
    _fields_ = (("dx",          wintypes.LONG),
                ("dy",          wintypes.LONG),
                ("mouseData",   wintypes.DWORD),
                ("dwFlags",     wintypes.DWORD),
                ("time",        wintypes.DWORD),
                ("dwExtraInfo", wintypes.ULONG_PTR))

class KEYBDINPUT(ctypes.Structure):
    _fields_ = (("wVk",         wintypes.WORD),
                ("wScan",       wintypes.WORD),
                ("dwFlags",     wintypes.DWORD),
                ("time",        wintypes.DWORD),
                ("dwExtraInfo", wintypes.ULONG_PTR))

    def __init__(self, *args, **kwds):
        super(KEYBDINPUT, self).__init__(*args, **kwds)
        # some programs use the scan code even if KEYEVENTF_SCANCODE
        # isn't set in dwFflags, so attempt to map the correct code.
        if not self.dwFlags & KEYEVENTF_UNICODE:
            self.wScan = user32.MapVirtualKeyExW(self.wVk,
                                                 MAPVK_VK_TO_VSC, 0)

class HARDWAREINPUT(ctypes.Structure):
    _fields_ = (("uMsg",    wintypes.DWORD),
                ("wParamL", wintypes.WORD),
                ("wParamH", wintypes.WORD))

class INPUT(ctypes.Structure):
    class _INPUT(ctypes.Union):
        _fields_ = (("ki", KEYBDINPUT),
                    ("mi", MOUSEINPUT),
                    ("hi", HARDWAREINPUT))
    _anonymous_ = ("_input",)
    _fields_ = (("type",   wintypes.DWORD),
                ("_input", _INPUT))

LPINPUT = ctypes.POINTER(INPUT)

def _check_count(result, func, args):
    if result == 0:
        raise ctypes.WinError(ctypes.get_last_error())
    return args

user32.SendInput.errcheck = _check_count
user32.SendInput.argtypes = (wintypes.UINT, # nInputs
                             LPINPUT,       # pInputs
                             ctypes.c_int)  # cbSize

# Functions

def PressKey(hexKeyCode):
    x = INPUT(type=INPUT_KEYBOARD,
              ki=KEYBDINPUT(wVk=hexKeyCode))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def ReleaseKey(hexKeyCode):
    x = INPUT(type=INPUT_KEYBOARD,
              ki=KEYBDINPUT(wVk=hexKeyCode,
                            dwFlags=KEYEVENTF_KEYUP))
    user32.SendInput(1, ctypes.byref(x), ctypes.sizeof(x))

def AltTab():
    """Press Alt+Tab and hold Alt key for 2 seconds
    in order to see the overlay.
    """
    PressKey(VK_MENU)   # Alt
    PressKey(VK_TAB)    # Tab
    ReleaseKey(VK_TAB)  # Tab~
    time.sleep(2)
    ReleaseKey(VK_MENU) # Alt~

if __name__ == "__main__":
    AltTab()

Unicode

From this stackoverflow

#include <vector>
#include <string>

void SendInputString(const std::wstring &str)
{
    int len = str.length();
    if (len == 0) return;

    std::vector<INPUT> in(len*2);
    ZeroMemory(&in[0], in.size()*sizeof(INPUT));

    int i = 0, idx = 0;
    while (i < len)
    {
        WORD ch = (WORD) str[i++];

        if ((ch < 0xD800) || (ch > 0xDFFF))
        {
            in[idx].type = INPUT_KEYBOARD;
            in[idx].ki.wScan = ch;
            in[idx].ki.dwFlags = KEYEVENTF_UNICODE;
            ++idx;

            in[idx] = in[idx-1];
            in[idx].ki.dwFlags |= KEYEVENTF_KEYUP;
            ++idx;
        }
        else
        {
            in[idx].type = INPUT_KEYBOARD;
            in[idx].ki.wScan = ch;
            in[idx].ki.dwFlags = KEYEVENTF_UNICODE;
            ++idx;

            in[idx].type = INPUT_KEYBOARD;
            in[idx].ki.wScan = (WORD) str[i++];
            in[idx].ki.dwFlags = KEYEVENTF_UNICODE;
            ++idx;

            in[idx] = in[idx-2];
            in[idx].ki.dwFlags |= KEYEVENTF_KEYUP;
            ++idx;

            in[idx] = in[idx-2];
            in[idx].ki.dwFlags |= KEYEVENTF_KEYUP;
            ++idx;
        }
    }

    SendInput(in.size(), &in[0], sizeof(INPUT));
}

Sending To A Window

From this stackoverflow

int SendKeystrokesToNotepad( const TCHAR *const text )
{
    INPUT *keystroke;
    UINT i, character_count, keystrokes_to_send, keystrokes_sent;
    HWND notepad;

    assert( text != NULL );

    //Get the handle of the Notepad window.
    notepad = FindWindow( _T( "Notepad" ), NULL );
    if( notepad == NULL )
        return 0;

    //Bring the Notepad window to the front.
    if( !SetForegroundWindow( notepad ) )
        return 0;

    //Fill in the array of keystrokes to send.
    character_count = _tcslen( text );
    keystrokes_to_send = character_count * 2;
    keystroke = new INPUT[ keystrokes_to_send ];
    for( i = 0; i < character_count; ++i )
    {
        keystroke[ i * 2 ].type = INPUT_KEYBOARD;
        keystroke[ i * 2 ].ki.wVk = 0;
        keystroke[ i * 2 ].ki.wScan = text[ i ];
        keystroke[ i * 2 ].ki.dwFlags = KEYEVENTF_UNICODE;
        keystroke[ i * 2 ].ki.time = 0;
        keystroke[ i * 2 ].ki.dwExtraInfo = GetMessageExtraInfo();

        keystroke[ i * 2 + 1 ].type = INPUT_KEYBOARD;
        keystroke[ i * 2 + 1 ].ki.wVk = 0;
        keystroke[ i * 2 + 1 ].ki.wScan = text[ i ];
        keystroke[ i * 2 + 1 ].ki.dwFlags = KEYEVENTF_UNICODE | KEYEVENTF_KEYUP;
        keystroke[ i * 2 + 1 ].ki.time = 0;
        keystroke[ i * 2 + 1 ].ki.dwExtraInfo = GetMessageExtraInfo();
    }

    //Send the keystrokes.
    keystrokes_sent = SendInput( ( UINT )keystrokes_to_send, keystroke, sizeof( *keystroke ) );
    delete [] keystroke;

    return keystrokes_sent == keystrokes_to_send;
}

Key Codes

From MSDN linked above.